A screen printing machine is incorporated in a production line of a printed circuit board (PCB) and is designed to perform screen printing of a conductive paste or the like on a substrate conveyed from upstream and to send the substrate to a downstream component mounting machine. In order to improve production efficiency, a screen printing machine has been developed as disclosed in Japanese Patent Application Laid-open No. 2009-70867 (Patent Document 1), for example, in which a pair of substrate supporting tables juxtaposed in a horizontal direction that intersects with a substrate conveying direction is provided in the machine and each substrate supporting table is provided with an print executing section. Such a screen printing machine has been developed so as to accommodate a so-called dual conveying-type component mounting machine which has two substrate conveying lines and which concurrently carries out (in parallel) component mounting on both conveying lines, and is intended to improve efficiency of a printing process in accordance with an increased speed of a component mounting process by coupling the screen printing machine and the component mounting machine with each other.
However, with the configuration according to Patent Document 1, a construction of each print executing section is unnecessarily redundant and wasteful. In other words, in cases where substrates of the same type are consecutively produced, the need to create two screen masks arranged with a same opening pattern results in an increased cost of screen masks. In addition, the need to prepare solder on each screen mask results in an excessive amount of solder necessary for preparation as well as a corresponding high cost of post-production solder treatment (disposal, storage, and the like). Furthermore, due to the redundant construction that combines the same print executing sections arranged to the left and right, enough space for arranging the respective print executing sections must be preserved. As a result, sizes of the machine itself as well as conveyors of an accompanying substrate sorting machine and the like tend to increase.